Mixing valves having the axial-angular or cylindrical coordinate modes of movement very often require complex seal structures. Some efforts have been made to provide simpler seal structures for valves of this class. One known valve utilizes a flexible cup that fits into a valve chamber so as to overlie diametrically disposed hot and cold water inlets. A valve stem fits into the cup and in the closed position of the valve presses the cup into sealing contact with the inlets. The stem, however, is relieved so that as the stem is moved axially outwardly, the cup, under the influence of line pressure, flexes radially inwardly to an extent determined by the degree of proximity of the stem surface. By suitable design of the stem surface, angular position and axial position determine proportion and volume.
While this known valve structure is quite simple in terms of essential structure and in terms of replacement of parts, the seal has certain undesirable characteristics. Thus the line pressure opposes the establishment of a seal whereby large forces must be imposed on the flexible cup at the regions of the inlet openings. This reduces the life of the seal member.
Our U.S. Pat. No. 3,661,181 discloses a mixing valve structure of the cylindrical coordinate class in which a seal element performs all of the dynamic and static seal functions in such manner that line pressure assists in the establishment of the seals. The seal element so disclosed is sleeve-like, a valve control stem extending through the element. The seal element provides two atria for hot and cold water ports, the atria being flexed under the influence of line pressure to assit in providing a seal when the control stem is positioned close to the corresponding atrium.
The single seal element, however, is somewhat complicated and expensive. Desirably, the seal element is simplified to make replacement inexpensive. Accordingly, the primary object of this invention is to provide an improved seal structure that operates in the same advantageous manner.